Interpretive Summary: Cultivated carrot is technically known by the scientific name Daucus carota. Cultivated carrot has about 20 related wild species known by other scientific names. Living collections of cultivated and wild carrot are useful in breeding programs to improve the appearance, disease resistance, and other useful traits in cultivated carrot. There are different ideas about how to classify the great variation found in wild collections of Daucus carota, and this creates confusion in the US genebank of carrot at the North Central Regional Plant Introduction Station in Ames Iowa that conserves about 1370 living collections, with about 1200 of these being D. carota. The purpose of our study was to use the form of the plant (morphological data) to investigate different ideas about how Daucus carota should be classified. Our study used 36 morphological characters from 155 living collections of D. carota and a few other similar wild species. This study was able to identify only two types of Daucus carota, bot the eight currently recognized in the genebank. These results, in combination with results from ongoing studies using molecular data are being used to reassess the practical identification of germplasm collections of D. carota. It will be useful not only to the genebank curators, but to carrot breeders who are using these collections in their breeding programs.

Technical Abstract:
The genus Daucus includes about 20 species. The most widespread and economically important species, Daucus carota L., occurs on almost every continent. Cultivated carrot, subsp. sativus (Hoffm.) Schubl. & G. Martens, has been selected from wild populations that are extremely diverse, especially in the western Mediterranean. Obligate outcrossing and lack of sexual isolating mechanisms among recognized infraspecific taxa complicate the taxonomy and identification of the wild populations, resulting in widely different interpretations of the number of infraspecific taxa. The US Daucus germplasm collection at the North Central Regional Plant Introduction Station (NCRPIS) in Ames, Iowa conserves about 1370 accessions, with about 1200 of these being D. carota. The purpose of our study was to explore morphological support for eight recognized subspecies of D. carota held at NCRPIS. We measured 36 morphological characters from multiple individuals within each of 155 accessions of D. carota, and the morphologically similar species D. capillifolius, alongside other species for comparison, in an experimental field plot. Within D. carota, multivariate analyses were able to identify only two subspecies, but even these showed great overlap of individual characters. In combination with molecular data and field collections, our goal is to reassess the practical identification of germplasm collections of D. carota.